🔧 chore: let→const for never-reassigned Sets/Maps/objects

ESLint prefer-const auto-fix: 12 variables changed from let to const
where the reference is never reassigned (Maps, Sets, sort state objects).

All tools clean:
- ESLint: 0 errors, 0 warnings
- Tests: 70/70 pass
- npm audit (runtime): 0 vulnerabilities

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

main.js

@@ -18,7 +18,7 @@ let dropTargetWindow = null;
 let tray = null;
 const configStore = new ConfigStore(app);
 let uploadManager = null;
-let folderMonitor = new FolderMonitor();
+const folderMonitor = new FolderMonitor();
 let remoteServer = null;
 let captureWindow = null;
 let captureWindowReady = false;

renderer/app.js

@@ -27,16 +27,16 @@ const AUTO_CHECK_PREF_KEY = 'autoHealthCheckBeforeUpload';
 
 // Queue state
 let queueJobs = []; // { id, file, fileName, hoster, status, bytesUploaded, bytesTotal, speedKbs, elapsed, remaining, error, result, attempt, maxAttempts, link }
-let _jobIndexById = new Map(); // id -> job (O(1) lookup)
+const _jobIndexById = new Map(); // id -> job (O(1) lookup)
-let _jobIndexByUploadId = new Map(); // uploadId -> job
+const _jobIndexByUploadId = new Map(); // uploadId -> job
-let selectedJobIds = new Set();
+const selectedJobIds = new Set();
 let _sessionTotalBytes = 0; // Total bytes ever added to queue this session
 let _sessionUploadedBytes = 0; // Bytes fully uploaded this session (done jobs)
-let _sessionTrackedJobs = new Set(); // Job IDs already counted for totalBytes
+const _sessionTrackedJobs = new Set(); // Job IDs already counted for totalBytes
-let _sessionDoneJobs = new Set(); // Job IDs already counted for uploadedBytes
+const _sessionDoneJobs = new Set(); // Job IDs already counted for uploadedBytes
-let _completedUploadKeys = new Set(); // 'filepath|hoster' keys for done uploads (survives removeFromQueueOnDone)
+const _completedUploadKeys = new Set(); // 'filepath|hoster' keys for done uploads (survives removeFromQueueOnDone)
-let _deletedJobIds = new Set(); // IDs of jobs explicitly deleted by user (prevents re-creation from stale progress callbacks)
+const _deletedJobIds = new Set(); // IDs of jobs explicitly deleted by user (prevents re-creation from stale progress callbacks)
-let queueSortState = { key: 'filename', direction: 'asc' };
+const queueSortState = { key: 'filename', direction: 'asc' };
 
 // History state
 let historyRowsData = [];
@@ -44,8 +44,8 @@ let historySortState = { key: 'date', direction: 'desc' };
 
 // Session-specific files for the "Files" panel (resets each session)
 let sessionFilesData = [];
-let recentSortState = { key: 'date', direction: 'desc' };
+const recentSortState = { key: 'date', direction: 'desc' };
-let selectedRecentIds = new Set();
+const selectedRecentIds = new Set();
 
 // --- Init ---
 async function init() {
@@ -2984,7 +2984,7 @@ function sortHistoryRows(rows) {
   const { key, direction } = historySortState;
   const factor = direction === 'asc' ? 1 : -1;
   return rows.slice().sort((a, b) => {
-    let cmp = key === 'date' ? a.dateTs - b.dateTs : _collatorDE.compare(String(a[key] || ''), String(b[key] || ''));
+    const cmp = key === 'date' ? a.dateTs - b.dateTs : _collatorDE.compare(String(a[key] || ''), String(b[key] || ''));
     return (cmp || a.order - b.order) * factor;
   });
 }